Forced-circulation hot water heating system

ABSTRACT

A hot water feed trunk runs from a gas fired water heater to a priority valve with branches from the priority valve to a radiator and to a heat exchanger respectively. Return branches from the heat exchanger and from the radiator join a return water trunk leading to the water heater and having a circulating pump therein. The priority valve includes a valve closure and a temperature responsive element positioned to be primarily responsive to cold service water (proceeding to the heat exchanger) and secondarily responsive to the temperature of the water from the feed trunk. When the element is comparatively cool, the feed water is sent to the heat exchanger. When the element is relatively hot, the feed water is sent to the radiator. A first switch closed by the flowing of service water is connected in series with a second switch so that when the two are closed the circulating pump will be energized and the valve controlling the gas flow to the burner will be opened. In one embodiment the second switch is controlled by the same element as actuates the valve closure. In another embodiment a second heat responsive element subjected to the same temperature conditions as the first controls the second switch.

States aten [54] FORCED-CIRCULATION HOT WATER HEATHNG SYSTEM [72]Inventor:

[73] Assignee:

[22] Filed:

Hans Meier, Remscheid, Germany Joli. Vaillant KG, Remscheid, GermanyAug. 7, 1970 [21] Appl.No.: 62,053

Primary Examiner-Edward J. Michael Mar. 7, 1972 AttorneyDarbo, Robertson& Vandenburgh [5 7] ABSTRACT A hot water feed trunk runs from a gasfired water heater to a priority valve with branches from the priorityvalve to a radiator and to a heat exchanger respectively. Returnbranches from the heat exchanger and from the radiator join a returnwater trunk leading to the water heater and having a circulating pumptherein. The priority valve includes a valve closure and a temperatureresponsive element positioned to be primarily responsive to cold servicewater (proceeding to the heat exchanger) .and secondarily responsive tothe temperature of the water from the feed trunk. When the element iscomparatively cool, the feed water is sent to the heat exchanger. Whenthe element is relatively hot, the feed water is sent to the radiator. Afirst switch closed by the flowing of service water is connected inseries with a second switch so that when the two are closed thecirculating pump will be energized and the valve controlling the gasflow to the burner will be opened. In one embodiment the second switchis controlled by the same element as actuates the valve closure. Inanother embodiment a second heat responsive element subjected to thesame temperature conditions as the first controls the second switch.

4 Claims, 2 Drawing Figures PATENTEUMAR 7 m2 SHEEY 1 OF 2 INVENTOR jgzvsMEIER PAIENTEDMAR 7 m2 SHEET 2 OF 2 INVENTOR Hqzvs MEIER BY M 6%? a?FORCED-CIRCULATION HOT WATER HEATING SYSTEM BACKGROUND AND SUMMARY OFTHE INVENTION The invention relates to an improvement and completion ofa prior system in which a thermostatically controlled priority valve hasits heat-sensing element cooled by incoming cold water of the servicewater'supply. The heat-sensing element of the priority valve is biasedby the feed or return water so that at temperatures below the desiredoperating temperature of the heating circuit the priority valve permitsa proportion of the feed water to enter the return line directly througha bypass (traversing the service water heat exchanger) instead ofadmitting it into heating circuit. When service water is drawn at a timewhen the hot feed water is flowing to the heating circuit, theheat-sensing element of the priority valve is intensively cooled byinflowing cold water so that a changeover of the priority valve takesplace very rapidly and all the feed water flows through the bypass inwhich the heat exchanger for service water heating is disposed.

In a system of this kind there are certain disadvantages in summeroperation when no water circulation in the heating circuit is takingplace and the system is used exclusively for heating service water. Uponthe completion of a draw of hot service water, the resultant stray heatin the system causes the heat-sensing element of the priority valve tobe heated so that said valve undesirably opens the inlet to the heatingcircuit until the stray heat is dissipated. Hot water circulation in theheating circuit therefore takes place if service water is once againwithdrawn during this period, although only for a short time.

It is the object of the invention to avoid the resultant heat loss ofsuch a prior art system. This is achieved in that a thermostaticallyelectric actuated switch is provided which controls the circulating pumpand also controls the gas supply to the burner, said switch beingcontrolled by the same temperature effects to which the heat-sensingelement of the priority valve is exposed.

To this end the system may be so arranged that the thermostatic switchis controlled by a separate second heat sensing element which is exposedto the same temperature conditions as the heat-sensing element of thepriority valve. To obtain reliable interlocking, the operatingtemperature of the two heatsensing elements is different with thearrangement being such that, in response to a drop in temperature, thevalve closes before the thermostatic switch closes. This temperatureoffset may not become effective in a clearly defined manner if thetemperature of the cold water supplied to the system when service wateris drawn off is substantially below the operating temperature of theheat sensing elements.

It is a further object of the invention in a system of the kinddescribed hereinbefore to obtain a simplified construction and to ensurethat the thermostatic valve closes reliably before the thermostaticswitch. This is achieved by employing a common heat-sensing element forthe priority valve and the thermostatic switch, which element will delaythe closing of the thermostatic switch relative to the closing of thepriority valve. The invention may, for example, be performed in that theheat-sensing element acts upon a rod which is guided through the valveclosure of the priority valve and sealingly through the housing of thevalve and is operatively connected to the thermostatic switch, the rodhaving an abutment which, after some travel following the opening of thethermostatic switch, contacts the valve closure and moves it in anopening sense. To this end, the thermostatic switch is connected inseries with a flow pressure switch, which responds to the flow ofservice water, so that the circuit of the solenoid valve and circulatingpump to be closed by the flow pressure switch is interrupted by thethermostatic switch for as long as the heat sensing elements areinsufficiently cooled.

DESCRIPTION OF THE DRAWINGS FIG. 1 diagrammatically illustrates aforced-circulation hot water system embodying the invention and usingtwo heat sensing elements; and

FIG. 2 diagrammatically illustrates a second embodiment in which onlyone heat sensing element is provided for the priority valve and thethermostatic switch.

DESCRIPTION OF SPECIFIC EMBODIMENTS The following disclosure is offeredfor public dissemination in return for the grant of a patent. Althoughit is detailed to ensure adequacy and aid understanding, this is notintended to prejudice that purpose of a patent which is to cover eachnew inventive concept therein no matter how others may later disguise itby variations in form or additions or further improvements. The claimsat the end hereof are intended as the chief aid toward this purpose, asit is these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.

The numeral 1 refers to the heat exchanger of a oncethrough water heatersupplied with heat by a gas burner 2. A heating circuit, containingradiators 5, is connected to the heat exchanger 1 by means of a feedtrunk 3 and a return trunk 4. A circulating pump 6 is incorporated intothe return 4. The feed 3 is connected to the inlet socket 7 of apriority valve 7. The feed branch 3', extending to the radiators 5, isconnected to a discharge socket 7 A connecting socket 8' of the priorityvalve 7 is provided for the branch feed 8 leading to the heat exchanger9. The heat exchanger 9 contains a pipe coil 9' in which service wateris heated. The return line 4 has branches to both the heat exchanger andthe radiator and a trunk in which the pump 6 is located.

Priority valve 7 has two opposed valve seats 10 and 11. Between them isa valve closure 12 urged toward seat 10 by a spring. Valve seat 10, inconjunction with closure 12, controls the flow from trunk 3 to branch 3'and in the same fashion seat 11 controls the flow to branch 8. Valveclosure 12 is connected to valve rod 13 also connected to temperaturesensitive element 14. Thus, the valve closure is positioned in responseto the temperature conditions applied to sensing element 14.

A cold water conduit 15 connects to a source of service water and to aconduit 16 of the priority valve 7. Valve 7 has an outlet socket 16'from conduit 16. Downstream of outlet socket 16' are the conduit 16'',the pipe coil 9' of the service water heater 9 and the tap valve 17through which the heated service water may be withdrawn. The duct 16surrounds the heat sensing element 14 of the thermostatic valve 12 sothat the element is cooled by the inflowing cold service water. To alesser extent the element 14 is influenced by the temperature of thewater from trunk 3 and flowing about the outside of conduit 16 while onits way to the space between opposed seats l0, 11.

A second heat sensing element 18 controls an electric thermostaticswitch 19 and is surrounded by the duct 16. An electric circuit extendsfrom M,,, R to the parallel connection of the circulating pump 6 and asolenoid valve 20 for controlling the gas supply to the burner 2. Thiselectric circuit has a branch 21 incorporating a room thermostat switch22 and a feed thermostat switch 23. A diaphragm system 24, responding tothe flow pressure, is connected to the cold water line 15 and operatesan electric switch 25 which is thus flow responsive. The flow responsiveswitch 25 and the thermostat switch 1? are serially connected in abranch 26 disposed in parallel to the branch 21 of the electric circuit.The gas valve 20 will be open and the pump 6 energized if (a) both ofswitches 22 and 23 are closed, or (b) both of switches 19 and 25 areclosed.

Assuming that the system is cold, the closure 12 of the priority valvewill be set as illustrated in FIG. 1 so that the flow from trunk 3proceeds to branch 8 and through the heat exchanger 9.

If the circulating pump 6 is then started and the burner 2 ignited,water, which is initially still cold, will flow from conduit 8 throughthe heat exchanger 9 and into the return 4. The heating circuitcontaining the radiators 5 is thus initially short circuited. The waterflowing through the bypass 8 and 9 is heated relatively rapidly. As theheating of the water progresses, the heat sensing element 14 moves thevalve clo-' sure 12 from its seat 10 so that an increasing part of thewater is admitted through the branch 3 into the heating circuit and theradiators 5. When the operating temperature of the hot waterforced-circulation heating system is reached, the valve closure 12contacts the valve seat 11 due to the action of the heat sensing element14 so that none of the circulating water enters the bypass 8, 9 and allwater accordingly must flow through the radiators 5. This function ofthe priority valve ensures that an adequate operating temperature of theforcedcirculation heating system can be reached as rapidly as possible,at first without dissipating any heat in the radiators 5 and that heatstorage in the service water heater 9 also takes place as rapidly aspossible.

If the tap valve 17 is opened for the withdrawal of service water whenthe forced-circulation hot water heating system is in the operativestate, that is to say when the opening through the valve seat 11 isclosed, it is desirable that all heat generated by the burner 2 beutilized for heating the service water. This is achieved by restoringthe bypass 8, 9 of the heating circuit 3', 5 and by at least partiallyshutting off the heating circuit. To this end, the cold water flowingthrough the duct 16 from the conduit 15 substantially cools the heatedheat sensing element 14 and overrides the influence thereon of the hotwater issuing from the feed 3. The effect of the cold water in the duct16 is so powerful that the heat sensing element 14 causes the valveclosure 12 to block the opening through the valve seat it) relativelyquickly and retains it in this position although heated water will thenissue from the heat exchanger 1 through the priority valve 7, the duct 8and the service water heater 9. Owing to the predominating effect of theinflowing cold water in the duct 16 on the heat sensing element 14, theservice water heating system is provided with priority relative to theheating circuit 3', 5, without the need for any mechanical or electricmotor driven changeover action of the valve closure 12. The priorityvalve 7 also functions as a water circulation regulating device by meansof which the circulation in the heating circuit 3', 5 is stopped orweakened so long as the normal operating temperature has not beenachieved.

During operation in summer, the solenoid valve and the circulating pump6 is switched off by the opening of switch 22 of the room thermostat. Ifservice water is then withdrawn from the tap valve 17, the heatresponsive element 18 is cooled (if it is not already cool) and closesswitch 19 and switch is closed by the flow of water being detected byflow-responsive device 24. The closing of these two switches opens thesolenoid valve 20 and turns on the circulating pump 6 for the durationof the draw of service water. On completion of the withdrawal operation,that is to say when no further cold water flows through the duct 15, theheat sensing element 14 will be heated due to the effect of the strayheat so that the closure 12 is raised from the seat 10. If service wateris once again withdrawn, a certain quantity of heated feed water wouldflow past closure 12- through the opening in valve seat 10 into theheating circuit 3', 5 which would result in an undesirable loss of heat.However, the stray heat influences not only the heat sensing element 14,but also, and to the same extent, the heat sensing element 18 so that itopens switch 19. With switch 19 open the closing of switch 25 will notactuate the solenoid valve 20 or the pump 6. These will only be actuatedafter the flow of service water through conduit 16 removes the strayheat and the heat-sensing elements 14, 18 are sufficiently cooled tomove closure 12 onto seat 10 and to close switch 19. Accordingly,reheating of the feed water is delayed in the event of renewedwithdrawal of service water while the service water heater is in the hotstate. The delay in reheating is hardly noticeable when withdrawingservice water owing to the presence of the service water heater (heatexchanger 9) which stores a certain quantity of heat. However, itprevents hot feed water temporarily being discharged into the heatingcircuit 3', 5 when the system is operated in summer.

The numeral 31 of FIG. 2 refers to the heat exchanger of a once-throughwater heater which is supplied with heat by a gas burner 32. A heatingcircuit, containing radiators 35, is connected to the heat exchanger 31by means of a trunk feed 33 and a trunk return 34. A circulating pump 36is incorporated into the return 34. The feed 33 is connected with theinlet socket 37' of a priority valve 37. The feed branch 33', extendingto the radiators, is connected to an outlet socket 37". A connectingsocket 38 of the priority valve 37 is provided for the connection of afeed branch conduit 38, leading to heat exchanger 39. Return branchesfrom the heat exchanger and the radiators lead to the return trunk 34.The heat exchanger 39 contains a pipe coil 39' in which the servicewater is heated.

A valve seat 40 is provided in the priority changeover device 37 in aposition between the connecting sockets 37 and 37". A second valve seat41 is disposed opposite to the valve seat 40 and is used (in conjunctionwith closure 42) to shut off flow to the connecting socket 38 fromsocket 37. A valve closure 42 is slideably guided on a valve stem 43 andis disposed between the opposed valve seats 40 and 41. The valve stem 43has an abutment forming a driver 45 which functions to force the valveclosure 42 from its seat 40 against the urging of spring 46. The valvestem 43 extends through the valve body with suitable packing (not shown)thereabout to provide a watertight seal through which the stem can move.The exterior end of the stem 43 actuates an electric switch 47. Thedriver 45 is positioned on the stem 43 at a spaced distance from thevalve closure 42 when the electric switch 47 is closed and the element44 is relatively cool. As the sensing element 44 is heated by water fromfeed 33, the switch 47 is therefore opened first and thereafter thevalve closure 42 is moved from the valve seat 40. A solenoid valve 48which controls the supplyof gas to the burner 32 and the circulatingpump 36 are connected in an electric circuit having a branch 49 whichincludes the switches 50 of a room thermostat and 51 of a feedthermostat. A flow-sensitive diaphragm system 53 is connected to thecold water duct 52 and actuates a flow sensitive switch 54. The flowswitch 54 and the thermostat switch 47 are connected in series in abranch 55 which is in parallel to the branch 49.

If, with the system cold, the circulating pump 36 is started and theburner 32 is ignited, the cold water in the system flows through thebranch 38 to the heat exchanger 39 and into the return 34. The heatingcircuit containing the radiators 35 is thus initially short circuited.The water circulating in the bypass 38 and 39 is heated relativelyrapidly. As this heated water flows through the priority valve 37 itinfluences heat sensor 44. With progressive heating of the water theheat sensing element 44 moves the valve stem downwardly to initiallyopen the switch 47. This isof no consequence for the operating conditionsince the supply of current to the valve 48 and the pump 36 ismaintained by branch 49 having closed switches 50 and 51. Furthermovement of the valve shank 43 causes the driver 45 to force the valveclosure 42 from its seat 40 toward seat 41 so that an increasing part ofthe circulating water is admitted via the branch 33' into the heatingcircuit and the radiators 35. When the operating temperature of the hotwater forced-circulation heating system is reached, the valve closure42, under the effect of the heat sensing element 44, closes the openingthrough valve seat 41 so that no further circulating water can pass viathe bypass 38, 39 into the return 34 and instead all water must flowthrough the radiators 35. This function of the priority valve results inan adequate operating temperature being rapidly established in theradiators 35 without any heat being dissipated and the storing of heatas rapidly as possible in the service water heater.

lf-the tap valve 56 is opened for the withdrawal of service water whenthe forced-circulation hot water heating system is in the operativestate, that is to say when the valve seat 41 is closed, it is desirablethat all heat produced by the burner 32 be utilized for heating theservice water; that is, it is desirable for the bypass of the heatingcircuit 33 35 to be reestablished via the conduit 38 and the heatexchanger 39. To this end, the cold water flowing through the conduit 57from the duct 52 rapidly cools the heated sensing element 44 andoverrides the influence thereon of the hot water issuing from the feed33. The inflow of the cold water in the conduit 57 is sufficientlyintense to enable the heat-sensing element 44 to rapidly retract valvestem 43. This results in the valve closure 42 rapidly closing theopening through the valve seat 40 and thereafter the switch 47 beingclosed. Both are retained in those positions although heated feed watercontinues to issue from the feed branch 33 and into the priority valve37 and then into the bypass 38, 39. Owing to the predominating influenceon the heat sensing element 44 of the influx of the cold water in theconduit 57, the service water heater 39 is therefore provided withpriority relative to the heating circuit 33 35 without the need for anymechanical or electric motor driven resetting of the valve closure 42.The priority valve 37, however, also performs'the function of aforced-circulation water regulating system by means of which thecirculation in the heating circuit 33 35 is either stopped or reducedfor as long as the operating temperature has not yet been reached.During operation in the summer, the solenoid valve 48 and thecirculating pump 36 are switched off by the switch 50 of the roomthermostat being open.

If service water is drawn off from the tap valve 56, the flow switch 54closes and if the sensing element 44 is not already cool, it is cooledby the flow of service water so that switch 47 is closed. This conditionestablishes an electric circuit through branch 55 to open solenoid valve48 and switch on the circulating pump 36 for the duration of the drawingoperation. On completion of the withdrawal operation, that is to saywhen no cold water continues to issue from the valve 56, the heatsensingelement 44 will be heated under the effect of stray heat in the priorityvalve. Thus, element 44 moves stem 43 to initially open switch 47 andsubsequently move the valve closure 42 away from the seat 40.

When service water is once again drawn, the switch 47 will preventstarting of the circulating pump 36 until after the thermostat valve 40,42 is closed to prevent any circulating water from flowing into theheating circuit 33 35. Reheating of the feed water is thus delayed ifservice water is withdrawn while the service water heater is still inthe hot state. The delay of reheating which accompanies the withdrawalof service water is hardly noticeable owing to the amount of heat storedby the service water heater 39. After closure 42 is against seat 40 andswitch 47 closes, there will be an electric circuit through branch 55 toopen gas valve 48 and energize pump 36.

I claim:

1. In a hot water heating system comprising a water heater with a gassupply valve having an electric operator, a radiator, a heat exchangerhaving two first connections for heating water and two secondconnections for service water, a service water conduit connected to thesecond connections, a feed line from the heater to one of the firstconnections on the heat exchanger and to the radiator, a return linefrom the other first connection and the radiator to the heater, acirculation pump in one of said lines, an electric circuit forenergizing the valve operator and circulation pump, and a priority valvedevice with a valve closure for controlling the flow from the waterheater to the heat exchanger in response to flow through the serviceconduit, temperature-responsive means positioned to respond to thetemperature of the water in the service conduit upstream of the heatexchanger and to the temperature of the water in the feed line from theheater with the influence of the service water thereon being greaterthan the influence of the feed water thereon, saidtemperature-responsive means being operatively connected to said valveclosure to operate said priority valve device, and an electric switch insaid electric circuit and operatively connected to thetemperature-responsive means to be actuated by said temperature-responsive means;

the improvement wherein said temperature responsive means comprisesheat-sensing means, actuating means operatively connecting the sensingmeans and the closure and the sensing means and the switch for closingthe switch with delay only after the closure has moved to a position toblock flow from the feed line to the radiator.

2. In a system as set forth in claim 1, wherein said heatsensing meanscomprises a single heat-sensing element.

3. In a system as set forth in claim 1, wherein said valve deviceincludes a valve body, a valve operating rod extending through the valvebody from the interior to the exterior thereof and in the interiorextends through said valve closure, means defining a valve seat and apassage from the seat to the radiator, spring means resiliently urgingsaid closure in a given direction toward said valve seat, means formingan abutment on said rod a spaced distance from said closure in saiddirection, said heat sensing means being connected to said rod to movethe rod longitudinally, said switch being positioned at the exterior ofsaid body to be operated by said rod.

4. In a system as set forth in claim 3, including a flowresponsiveactuator connected in said service conduit to respond to the flowtherein, said actuator including an electric switch which is closed inresponse to flow in said service conduit, said electric switches beingconnected in series in said circuit so that when both are closed thecirculating pump and the valve operator are energized.

Attesting Officer UNE'EEDSTATES PATENT oFFitE he E3 W CATE 0F (:0 MM???i ON Patent No. 3 a 136 Dated March 7 19.72;

Inventor(s) Hans Meier It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

111193, "33" should be --33'-- line 18 "33" should be; --33 '---Y line23, "33" shou ld b'e :33 line 43, "33" should be --33 Column '5, Column5, Column 5,

Column 5,

Signed and sealed this 18th day of December 1973 (SEAL) At'test:

.RENE D. TEGTMEYER J EDWARD Mo FLETCHER, JR. 7

- Acting Commissioner of Patents

1. In a hot water heating system comprising a water heater with a gassupply valve having an electric operator, a radiator, a heat exchangerhaving two first connections for heating water and two secondconnections for service water, a service water conduit connected to thesecond connections, a feed line from the heater to one of the firstconnections on the heat exchanger and to the radiator, a return linefrom the other first connection and the radiator to the heater, acirculation pump in one of said lines, an electric circuit forenergizing the valve operator and circulation pump, and a priority valvedevice with a valve closure for controlling the flow from the waterheater to the heat exchanger in response to flow through the serviceconduit, temperature-responsive means positioned to respond to thetemperature of the water in the service conduit upstream of the heatexchanger and to the temperature of the water in the feed line from theheater with the influence of the service water thereon being greaterthan the influence of the feed water thereon, saidtemperature-responsive means being operatively connected to said valveclosure to operate said priority valve device, and an electric switch insaid electric circuit and operatively connected to thetemperature-responsive means to be actuated by saidtemperature-responsive means; the improvement wherein said temperatureresponsive means comprises heat-sensing means, actuating meansoperatively connecting the sensing means and the closure and the sensingmeans and the switch for closing the switch with delay only after theclosure has moved to a position to block flow from the feed line to theradiator.
 2. In a system as set forth in claim 1, wherein saidheat-sensing means comprises a single heat-sensing element.
 3. In asystem as set forth in claim 1, wherein said valve device includes avalve body, a valve operating rod extending through the valve body fromthe interior to the exterior thereof and in the interior extends throughsaid valve closure, means defining a valve seat and a passage from theseat to the radiator, spring means resiliently urging said closure in agiven direction toward said valve seat, means forming an abutment onsaid rod a spaced distance from said closure in said direction, saidheat sensing means being connected to said rod to move the roDlongitudinally, said switch being positioned at the exterior of saidbody to be operated by said rod.
 4. In a system as set forth in claim 3,including a flow-responsive actuator connected in said service conduitto respond to the flow therein, said actuator including an electricswitch which is closed in response to flow in said service conduit, saidelectric switches being connected in series in said circuit so that whenboth are closed the circulating pump and the valve operator areenergized.